Effects of l -carnitine infusions on inflammatory and nutritional markers in haemodialysis patients

Abstract

Background. Carnitine loss through dialysis membranes is shown to be related to the lack of carnitine in long-term haemodialysis patients. It has been previously reported that haemodialysis patients might have benefited from carnitine supplementation.

Methods. A total of 21 chronic haemodialysis patients maintaining carnitine supplementation and 21 controls (haemodialysis patients not receiving carnitine) were included in the study. l -carnitine was used intravenously three times a week after each haemodialysis session, at a 20 mg/kg dose. C-reactive protien (CRP), lipid profile, transferrin, total protein and albumin levels were determined at baseline after 3 and 6 months of treatment, and compared with the control group.

Results. CRP levels were significantly decreased in carnitine group in contrast to the increase in the control group. Transferrin, total protein and albumin levels and body mass index (BMI) of the patients rose in the carnitine group.

Conclusions. There was a significant benefit of l -carnitine on CRP, transferrin, total protein and albumin levels of the haemodialysis patients.

CRP, haemodialysis, inflammation, l -carnitine , nutrition

Introduction

Today, the primary aim is not only the survival of haemodialysis patients but also to increase the quality of life. Additional treatment protocols are put into practice for this purpose and carnitine can also be included in this group. One of the most important complications is of cardiovascular origin, and the risk of cardiovascular disease in patients with chronic renal disease is far greater than in the general population [ 1 ]. The common risk factors for atherosclerosis are not enough to explain this high proportion and the uraemic syndrome appears to play an important role [ 2 ]. It has shown that coronary atherosclerosis can develop even in the age of 20s in patients with end-stage renal disease [ESRD] [ 3 ]. Local vascular inflammation is an important factor for atheroscleosis; C-reactive protein (CRP) is an objective index for inflammation and, therefore, suppression of CRP is important.

Carnitine is a small molecule, which is important in the β-oxidation of fatty acids. Insufficient carnitine synthesis, and especially its loss during dialysis, can cause a lack of carnitine in haemodialysis patients. Scattered reports indicate that l -carnitine may suppress pro-inflammatory cytokines, improve protein synthesis or nitrogen balance and may have effects on lipid parameters and erythropoietin (rHuEPO) requirements.

CRP is a positive acute phase protein that is increased in inflammation. Inflammatory stimuli cause the release of cytokines like interleukin (IL-1), IL-6 and tumour necrosis factor-α (TNFα), and these cytokines increase the synthesis and release of CRP [ 4 ]. CRP level is an objective index, which shows the pro-inflammatory cytokine generation and is widely accepted as an independent cardiovascular risk marker. It has been previously reported that carnitine treatment may suppress CRP levels in haemodialysis patients [ 5 ], but data in this field are sparse. In the present study, we performed a prospective, randomized and controlled trial to test the influence of carnitine supplementation on CRP, lipid profile, transferrin, total protein and albumin levels in haemodialysis patients.

Subjects and methods

Patients and controls

The study was performed in a single centre. A total of 42 haemodialysis patients from the same dialysis unit were included in the study. Patients were asked to participate if they were undergoing haemodialysis at least three times a week and had not received any l -carnitine treatment in the previous 6 months. Patients were randomly assigned to either the carnitine or control group by systematic random sampling method as described [ 6 ]. A total of 21 patients were scheduled to take l -carnitine supplementation (44.0 ± 13.9 years; 13 men and 8 women) (group 1) and the rest of the patients were served as the control group and observed without supplementation with l -carnitine (43.4 ± 13.9 years; 11 men and 10 women) (group 2). We did not choose a double-blind study design because all of the observed parameters were objective laboratory data. The tests were made at the baseline, 3 and 6 months after the carnitine treatment for both of the groups simultaneously ( Figure 1 ). The dialysis programme of the patients was 4 h three times a week using polysulphane hollow-fibres membranes (Fresenius Medical Care, Bad Homburg, Germany) and bicarbonate dialysate. l -carnitine (Santa Farma, Pomezia, Italy) was used intravenously three times a week after each haemodialysis session, at a 20 mg/kg dose. The underlying causes of ESRD were glomerulonephritis, hypertensive nephropathy, diabetic nephropathy and tubuluinterstitial nephritis in 8, 4, 5 and 2 patients in group 1, and 7, 5, 4 and 2 patients in group 2, respectively. Additionally, one patient from group 1 had IgA nephropathy and two patients developed ESRD due to amiloidosis and one patient after obstructive nephropathy in group 2. Duration of dialysis was 4.2 ± 2.9 years in group 1 and 2.3 ± 1.9 years in group 2. Plasma total and free carnitine levels were measured before and 6 months after the treatment. All of the patients and controls were informed and the study was approved by the Local Ethics Committee of our hospital.

Fig. 1.

CRP levels of the patients in ( A ) carnitine group and ( B ) control group.

Biochemical analyses

Samples were obtained before the dialysis session and stored at −20°C until the analysis.

CRP was measured with a Beckman Coulter nephelometer. Total protein, albumin, total cholesterol, triglycerides and high density lipoprotein (HDL) cholesterol were determined in a Roche Modular P analyser with the original reagents. Low density lipoprotein (LDL) levels were calculated using the Friedewald formula [ 7 ]. Transferrin was calculated using serum iron binding capacity with a conversion factor of 0.70. Total and free carnitine levels were measured as described by Wan and Hubbard [ 8 ]. With this method, l -carnitine reacts with acetyl CoA catalysed by carnitine acetyltransferase to form acetyl l -carnitine and CoASH. CoASH reacts non-enzymatically with 5,5′-dithiobis-2-nitrobenzoate to form 5-thio-2-nitrobenzoate (TNB). The concentration of TNB is measured spectrophotometrically at 410 nm. Body mass index (BMI) was calculated using standard techniques.

Statistical analysis

Values are presented as mean ± SD, with a P -value <0.05 indicating significance. Baseline clinical variables were compared using the t -test between groups. The evolution of clinical parameters was analysed in both groups by repeated-measures analysis of variance (ANOVA). All statistical calculations were made using SPSS® for Windows 14.0 (SPSS Inc. Headquarters, Chicago, lL, USA) software program.

Results

Serum free carnitine levels were 26.8 ± 9.8 and 134.6 ± 75.2 µmol/l; total carnitine levels were 39.2 ± 17 and 150.4 ± 73.3 µmol/l before and after carnitine treatment, respectively ( P < 0.001; P < 0.001). Mean ± SD levels of the biochemical parameters are shown in Table l. Serial changes in clinical parameters were analysed by repeated-measures ANOVA in both of the groups. In the carnitine-treated group, serial changes in CRP, tryglicerides, total protein, albumin and transferrin were statistically significant ( P = 0.007, <0.001, <0.001 and <0.001, respectively). In the control group, CRP was increased significantly ( P = 0.001). There was not a significant change in total protein, albumin and transferrin levels. According to the statistical analysis, we were able to show significant improvements in CRP, total protein, albumin and transferrin levels in group 1. In group 2, no significant improvement was observed in CRP and total protein, albumin and transferrin levels and thus the improvements in group 1 can be interpreted as caused by carnitine supplementation ( Table 1 ). Lipid parameters were affected in both of the groups. This effect was probably due to factors such as diet, exercise, etc. and was not connected to l -carnitine treatment as it was also observed in the control group. White blood cell count did not show any significant change in either of the groups. BMI was significantly increased in group 1 ( P < 0.001), and no significant change was observed in group 2.

Table 1.

Influence of l -carnitine on serum CRP, serum lipids and nutritional parameters

	Baseline (Mean ± SD)			3 months (Mean ± SD)		6 months (Mean ± SD)		P (ANOVA)
	Group 1	Group 2		Group 1	Group 2	Group 1	Group 2	Group 1	Group 2
CRP (mg/dl) [Median (min/max)]	0.87 (0.10/5.52)	0.67 (0.01/8.05)	NS	0.35 (0.017/4.37)	0.80 (0.01/8.05)	0.17 (0.01/3.37)	1.60 (0.30/13.7)	0.007	0.001
Serum lipids
Total cholesterol (mmol/l)	4.0 ± 0.8	4.8 ± 1.7	NS	3.7 ± 0.9	4.8 ± 1.6	3.8 ± 0.8	4.3 ± 1.3	NS	0.007
Tryglicerides (mmol/l)	1.6 ± 0.6	1.9 ± 1.2	NS	2.0 ± 0.7	1.8 ± 0.8	1.5 ± 0.7	1.6 ± 0.8	0.001	NS
LDL cholesterol (mmol/l)	2.1 ± 0.8	2.9 ± 1.1	P < 0.05	1.9 ± 0.8	2.8 ± 1.2	2.1 ± 0.6	2.6 ± 1.1	NS	NS
Nutrition/inflammation
Total protein (g/l)	64 ± 5	66 ± 11	NS	68 ± 5	65 ± 13	69 ± 5	64 ± 14	<0.001	NS
Albumin (g/l)	36 ± 3	35 ± 9	NS	39 ± 2	34 ± 9	41 ± 3	34 ± 9	<0.001	NS
Transferrin (g/l)	1.2 ± 0.2	1.7 ± 0.4	P < 0.05	1.4 ± 0.3	1.6 ± 0.5	1.6 ± 0.4	1.5 ± 0.5	<0.001	NS
BMI (kg/m 2 ) a	23.4 ± 4.01	21.5 ± 3.53	P < 0.05	23.7 ± 4.08	21.4 ± 3.41	23.7 ± 4.04	21.4 ± 3.43	<0.001	NS
Body weight (kg) a	62.8 ± 12.6	62.0 ± 12.9	NS	63.6 ± 12.8	61.7 ± 12.5	63.8 ± 12.6	61.7 ± 12.6	<0.001	NS
WBC (10 3  µl)	7.66 ± 1.70	7.35 ± 3.20	P < 0.05	7.12 ± 1.70	7.89 ± 2.91	7.14 ± 1.91	7.50 ± 2.63	NS	NS
UF during dialysis (ml)	2819 ± 802	1976 ± 1070	P < 0.05	2885 ± 833	2090 ± 1028	3138 ± 858	2061 ± 987	<0.001	NS
Blood pressure (sistolic) a	12.9 ± 1.81	13.2 ± 1.53	NS	12.7 ± 1.65	12.9 ± 1.50	13.1 ± 1.98	12.8 ± 1.78	NS	NS
Blood pressure (diastolic) a	8.01 ± 1.47	7.93 ± 0.81	NS	8.48 ± 1.45	7.76 ± 1.41	8.10 ± 1.45	7.98 ± 1.23	NS	NS

^a Considered after the dialysis session.

Discussion

l -carnitine levels are ∼50% increased in ESRD before haemodialysis compared with healthy controls because of the decreased renal excretion and the accumulation of carnitine. Carnitine levels begin to decrease after the beginning of haemodialysis [ 9 ]. It has been known that plasma and tissue carnitine levels are significantly decreased in long-term haemodialysis patients. The main reason for this is the removal of carnitine with dialysis. Carnitine is a small water-soluble molecule and it is freely dialysed; this property causes haemodialysis patients to have a predisposition for carnitine deficiency. Carnitine levels of the haemodialysis patients were also reduced, as expected in our study. The decrease in plasma carnitine levels of chronic haemodialysis patients is obtained by the transition from mainly the liver and from muscle in less amounts. Transition of l -carnitine from the liver to plasma is easier, whereas, it is much more difficult from muscle to plasma. For this reason, plasma carnitine levels do not accuratetly reflect tissue levels [ 9 ].

Many studies have shown that l -carnitine supplementation leads to improvements in several conditions seen in uraemic patients. There are reports that show an improvement in subjective complaints like muscle pains, cramps, exhaustion and fatigue [ 10 , 11 ] in addition to other reports on recovery in laboratory parameters [ 12–14 ].

There are studies reporting the positive effects of carnitine in terms of nutritional parameters [ 5 ] despite other studies indicating no significant benefit [ 15 ]. The increase of total protein, albumin and transferrin might be caused by improved anabolic effects or anti-inflammatory activities of l -carnitine, in the present study. Albumin and transferrin are known as negative acute-phase proteins and their synthesis is suppressed in inflammation probably by pro-inflammatory cytokines [ 16 ]. The decrease in CRP levels with l -carnitine supplementation is consistent with this possibility. However, the possibility that the synthesis of albumin and transferrin might be increased by the improved nutritional intake cannot be ruled out and the increase in BMI supports this idea.

CRP is a positive acute phase protein that is increased in inflammation. Inflammatory stimuli cause the release of cytokines like IL-1, IL-6 and TNFα, and these cytokines increase the synthesis and release of CRP [ 4 ]. CRP level is an objective index, which shows the pro-inflammatory cytokine generation and is widely accepted as an independent cardiovascular risk marker. It has been previously reported that CRP levels increase in dialysis patients [ 17–19 ] and a positive correlation with cardiovascular events has also been shown [ 20–22 ]. In this study, we showed that CRP levels may be decreased with carnitine treatment. There are a few reports supporting the hypothesis that treatment with l -carnitine has improved the chronic inflammation in haemodialysis patients in recent years [ 5 , 23 ]. There are only few studies reporting the effect of l -carnitine on CRP levels of haemodialysis patients [ 5 ] and this controlled study supports these findings.

In conclusion, we showed that carnitine treatment may have significant benefits on CRP, total protein, albumin and transferrin levels in haemodialysis patients. These factors are related with the mortality and morbidity of these patients, and are especially important in this regard. The results need to be confirmed in a larger patient population with the long-term follow-up.

Conflict of interest statement . None declared.